Tere,
I have a two queen colony.  It's called a Kerkoff (sp?) It has two separate
hive bodies one facing opposite of each other.  The difference is that above
the queen excluders of each hive they both share the same honey shallows for
surplus honey.  the pheromones (sp?) of both hives mix so there isn't any
fighting of the two hives.  This works out very well since they make honey
like crazy.  I'll send you a photo of it if you would like.  They are made in
Canada and cost about $300.00 US dollars for the basic hive.  I would have
more then one if I could afford it.